Added helper class Referencable (a simple base class for reference counting).

git-svn-id: file:///srv/svn/repos/haiku/trunk/current@11028 a95241bf-73f2-0310-859d-f6bbb57e9c96

src/servers/registrar/Referencable.cpp

@@ -0,0 +1,41 @@
+// Referencable.cpp
+
+#include "Debug.h"
+#include "Referencable.h"
+
+// constructor
+Referencable::Referencable(bool deleteWhenUnreferenced)
+	: fReferenceCount(1),
+	  fDeleteWhenUnreferenced(deleteWhenUnreferenced)
+{
+}
+
+// destructor
+Referencable::~Referencable()
+{
+}
+
+// AddReference
+void
+Referencable::AddReference()
+{
+	atomic_add(&fReferenceCount, 1);
+}
+
+// RemoveReference
+bool
+Referencable::RemoveReference()
+{
+	bool unreferenced = (atomic_add(&fReferenceCount, -1) == 1);
+	if (fDeleteWhenUnreferenced && unreferenced)
+		delete this;
+	return unreferenced;
+}
+
+// CountReferences
+int32
+Referencable::CountReferences() const
+{
+	return fReferenceCount;
+}
+

src/servers/registrar/Referencable.h

@@ -0,0 +1,109 @@
+// Referencable.h
+
+#ifndef REFERENCABLE_H
+#define REFERENCABLE_H
+
+#include <SupportDefs.h>
+
+// Referencable
+class Referencable {
+public:
+								Referencable(
+									bool deleteWhenUnreferenced = false);
+	virtual						~Referencable();
+
+			void				AddReference();
+			bool				RemoveReference();	// returns true after last
+
+			int32				CountReferences() const;
+
+protected:
+			vint32				fReferenceCount;
+			bool				fDeleteWhenUnreferenced;
+};
+
+// Reference
+template<typename Type>
+class Reference {
+public:
+	Reference()
+		: fObject(NULL)
+	{
+	}
+
+	Reference(Type* object, bool alreadyHasReference = false)
+		: fObject(NULL)
+	{
+		SetTo(object, alreadyHasReference);
+	}
+
+	Reference(const Reference<Type>& other)
+		: fObject(NULL)
+	{
+		SetTo(other.fObject);
+	}
+
+	~Reference()
+	{
+		Unset();
+	}
+
+	void SetTo(Type* object, bool alreadyHasReference = false)
+	{
+		Unset();
+		fObject = object;
+		if (fObject && !alreadyHasReference)
+			fObject->AddReference();
+	}
+
+	void Unset()
+	{
+		if (fObject) {
+			fObject->RemoveReference();
+			fObject = NULL;
+		}
+	}
+
+	Type* Get() const
+	{
+		return fObject;
+	}
+
+	Type* Detach()
+	{
+		Type* object = fObject;
+		fObject = NULL;
+		return object;
+	}
+
+	Type& operator*() const
+	{
+		return *fObject;
+	}
+
+	Type* operator->() const
+	{
+		return fObject;
+	}
+
+	Reference& operator=(const Reference<Type>& other)
+	{
+		SetTo(other.fObject);
+		return *this;
+	}
+
+	bool operator==(const Reference<Type>& other) const
+	{
+		return (fObject == other.fObject);
+	}
+
+	bool operator!=(const Reference<Type>& other) const
+	{
+		return (fObject != other.fObject);
+	}
+
+private:
+	Type*	fObject;
+};
+
+#endif	// REFERENCABLE_H